Abstract
After the nuclear accident in Chernobyl in 1986, environmental effects of radiation appeared remarkably in conifers such as pine and spruce trees in the surrounding forests. It was in striking contrast to deciduous trees such as birch, which showed much less damages in the forests. Depending on the exposed radiation levels, the conifers showed growth inhibition, malformation of needles, reproductive loss and withering, which mainly resulted from cellular damages in proliferating points, meristem, in apical buds and root tips. For investigations of radiation effects on the proliferating cells in plants, in vitro cell cultures must be as powerful as it is for investigation of proliferating cells in mammals. In this study, suspension cell cultures of Japanese native conifers, Japanese cedar (Cryptomeria japonica) and Japanese larch (Larix kaempferi) were used to elucidate cellular effects of ionizing radiation on conifers. Cell proliferation in the suspension cultures was inhibited significantly by acute irradiation with X-rays at doses above 0.5 Gy or chronic irradiation with gamma-rays at doses above 120 mGy / day. These results show that the coniferous cells are highly sensitive to both acute and chronic irradiations and therefore useful to analyze cellular mechanisms relating to the radiation damages in coniferous plants around the Chernobyl power plant.
